Many medical procedures require that medical personnel gain percutaneous access to the vascular system of a patient. Percutaneous access is achieved when a wire guide is positioned in the lumen of a blood vessel for permitting a dilator and introducer sheath to be positioned thereover and introduced into the vessel lumen. One technique for gaining vascular access is the Seldinger technique, which requires holding a hollow bore needle in a vessel of the vascular system while inserting a wire guide therethrough. Once the wire guide is positioned in the vessel and the needle is removed, a dilator and sheath are positioned over the wire guide and inserted into the vessel lumen. A problem with this technique is that it requires that medical personnel performing the procedure have significant dexterity and experience in performing the technique. It is difficult to keep the needle positioned in the vessel lumen. If the position of the needle changes, it may extend into the connective tissue surrounding the vessel and cause trauma to the access site. Furthermore, if the needle is positioned in connective tissue and the medical person inserts the wire guide therethrough, the wire guide damages the connective tissue surrounding the vessel. As a result of injury to the access site, medical personnel will have to find another access site. However, some patients do not have another viable access site. Another problem with this technique is that the wire guide is thin, flexible, and smooth, therefore difficult and time consuming to manipulate and guide through the needle. While insertion is being attempted, blood is typically spurting out of the introducer needle and contaminating the surgical field. This is of particular concern in view of the HIV virus and AIDS. Still another problem with this technique is that the wire guide may be sheared off by the metal needle, leaving a piece of the wire guide in the patient's body. Wire guides with a J-shaped or increasingly flexible distal end are particularly susceptible to shearing.
Another technique for gaining percutaneous vascular access uses over-the-needle catheters. Using the over-the-needle technique, a needle with a catheter positioned thereover is positioned in a vessel lumen. The catheter is pushed over the needle into the vessel lumen, and the needle is removed. Then a wire guide is positioned through the catheter, which is less likely to shear off the wire guide than a metal needle. A problem with this technique is that, again, manipulation of the wire guide is difficult and time consuming. In emergency and critical care situations, time delays may be life threatening. Furthermore, the process of feeding the wire guide into the vessel lumen through the catheter can be interrupted by an emergency push of medication or fluid. When this happens, the wire guide has to be completely removed from the catheter. Then vascular access is attempted at another site, if another access site is viable, or delayed until the introduction of fluid can be stopped or interrupted long enough to reinseft the wire guide and position a dilator and sheath in the vessel. Another problem with this technique is that the over-the-needle catheter has a small diameter for being positioned over the needle. As a result, the lumen is too small for permitting the introduction of a large volume of fluid such as the amount required to treat a patient suffering from hypovolemic shock.